If you ban people in the back of pickups you have to ban many other types transportation. Like the flimsy motorcycle side cars, no more than two on a motorcycle etc, no more travelling on top of trucks, no more school children hanging off the back of songthews, the list goes on and on and nothing is going to change and the carnage will continue until the people in charge of transporting people start treating people as humans and not animals. I have a video somewhere of a pickup converted into a double decker to enable it to carry about 20 workers.
Many times workers travelling in the back of pickups is done to save money and greatly increase profits.